The focus of the proposal is to study physical mechanisms involved in the complex reorganization of the cell surface during lymphocyte adhesion and activation. The formation of the immune synapse facilitates communication between T-cells and antigens presenting cells, allowing the T-cell to become activated for immune response. The junction of the immune synapse has been recognized as a highly organized structure, able to redistribute certain receptors to particular regions of the junction. The spatial regulation of receptors included and excluded from the synapse is not well understood, however, and the motion of these receptors has not been systematically studied. Our proposed studies will use single particle tracking to examine the motion of individual LFA-1, CD43 and CD45 receptors on resting and activated T-cells. Additionally, we intend to develop calibration standards for single particle tracking experiments using artificial surfaces. These surfaces will provide a readily available standard for experiments studying anomalous diffusion. Together, these studies will provide a more detailed understanding of the molecular events that control immune synapse structure and function.